The C63 is louder. The C63 has a firmer ride. Other than a nice looking interior, I would say the C63 is LESS luxury.

IMO the M3 is actually the more comfortable car to drive day to day. The C63 isn't uncomfortable by any means but the M3 is better. One thing the M3 does really well (among others) is that it can go from being very docile to a screamer... the C63 is more intense all of the time which isn't necessarily always a good thing. It's great when you want to play a bit and have fun but not as good for the days you just want to relax and cruise home.

I'm curious why you would say the C63 is more luxurious other than that would be the reputation that MB would have as a company?

P.S. I am now only ever going to post when I can put down the C63... otherwise, I'm staying quiet

It is not more luxurious, just more luxury feel getting in the way when trying to track the car. To be more specific, it doesn't marriage the cars handling with power. Hence the reason I stated that it seemed like an afterthought. IMO